The invention pertains broadly to x-ray techniques used to analyze materials, and in particular techniques based on x-ray fluorescence.
X-rays have for some time been used to probe and characterizer materials, in particular to probe a material's atomic structure by x-ray absorption fine structure analysis. By this technique, a sample is exposed to a monochromatic x-ray beam, and the absorption of the beam measured by comparing the beam's input and throughput intensities (i.e. input and throughput power). By repeating this for different energies (frequencies) of x-rays, one generates the material's absorption spectrum, whose signature is characteristic of the atomic structure within the material. Because an x-ray beam that completely traverses the sample is necessary for this technique, the technique is limited to use with thin samples. This limitation led to the development of another system useful with thicker, more absorptive, samples, in which fluorescence induced by a monochromatic x-ray beam is measured over a spectrum of frequencies to map out a fine structure curve for a sample. Heretofore, however, the use of such schemes have been limited to identifying fine structure, and other techniques used to identify directly the specific elemental constituents of a sample (i.e. to do qualitative elemental analysis) and the amount of these elements present (quantitative elemental analysis). Additionally, because detection of fluorescent photons is, in effect, a counting process, the lower the power of the exciting x-ray beam the fewer the number of resultant fluorescences generated in response, hence the poorer the detection statistics, and the longer the detection process must be run in order to generate useful data. To decrease this time, one must either increase the intensity (power) of the exciting x-ray beam, or increase the sensitivity of the fluorescence detector, the latter effectively meaning that one must use a more sensitive, i.e. complicated and expensive, detector.